
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>弹出层效果</title>
<style>
html,body{height:100%;overflow:hidden;}
body,div,h2{margin:0;padding:0;}
body{font:12px/1.5 Tahoma;}
center{padding-top:10px;}
button{cursor:pointer;}
#overlay{position:absolute;top:0;left:0;
    width:100%;height:100%;background:#000;
    opacity:0.5;filter:alpha(opacity=50);/* 透明度固定写法：opacity：透明效果，filter：alpha(opacity==50):兼容ie8以下 */
    display:none;}
#win{position:absolute;top:50%;left:50%;width:400px;height:200px;background:#fff;border:4px solid #f90;
    margin:-102px 0 0 -202px;display:none;}
h2{font-size:12px;text-align:right;background:#FC0;border-bottom:3px solid #f90;padding:5px;}
h2 span{color:#f90;cursor:pointer;background:#fff;border:1px solid #f90;padding:0 2px;}
</style>
<script>
window.onload = function ()
{
	var oWin = document.getElementById("win");
	var oLay = document.getElementById("overlay");	
	var oBtn = document.getElementsByTagName("button")[0];
	var oClose = document.getElementById("close");
	oBtn.onclick = function ()
	{
		oLay.style.display = "block";
		oWin.style.display = "block"	
	};
	oClose.onclick = function ()
	{
		oLay.style.display = "none";
		oWin.style.display = "none"	
	}
};
</script>
</head>
<body>
<div id="overlay"></div>
<div id="win"><h2><span id="close">×</span></h2></div>

<center><button>弹出层</button></center>
</body>
</html>
